Spark plug construction



Dec. 1, 1936. A. Q H F 2,062,514

SPARK PLUG CONSTRUCTION Filed Feb. 19, 1935 1 N VEN TOR. Ana/501v C HoarATTORNEY.

Patented Dec. 1, 1936 SPARK PLUG CONSTRUCTION Addison H001, Hinsdale,lllL Application February 8 Claims.

My invention relates to improvements in spark plugs and like devices.

My invention relates more particularly to improvements in theconstruction of spark plugs for internal combustion engines such as areused in automobiles; aeroplanes and motor boats.

One of the objects of my invention is to produce a new and usefulelement of a spark plug,

manipulation only when submitted to temperature much higher than thatever attained within the cylinder of an internal combustion engine.

A further object of the invention is to provide an insulator havingpractically the same coefficient of expansion as the metal conductor sothat cracking of the insulator due to changes in temperature will beavoided.

During recent years an extensive investigation has been made todetermine whether or not castings could be madefrom basaltor otherigneous rocks. This investigation covered a development whereby anigneous rock may be melted, cast to desired shape, and by proper heattreatment devitrified, to form a material possessing good electricalinsulation qualities and high mechanical strength.

Various objects of cast basalt such as building cornices, corner stonesand paving blocks, have been made in England and France, using someform'of a devitrifying process since 1700, and

stone bottles since as early as 1600.

Basalt is a form of igneous-rock widely distributed on the earthssurface, heavy, dark colored, hard, and very fine grained. It is not amineral of definite constitution, but a mixture of several, generallylabradorite, augite, olivine and magnetite.

Basalt melts between 1200 and 1400 degrees C. and may be poured into amold. If allowed to cool rapidly it becomes a jet black glass quitesimilar to obsidian, very brittle and subject to high internal stresses.With several hours heat treatment at 800 to 1000 degrees C. a castingdevitrifies int a tough material showing a fracture of very much thesame appearance as th orig- 19, 1935, Serial No. 3,230

inal rock. It has a good electrical resistance and ability to enduresevere mechanical shocln An igneous rock'is a solidification of moltenmatter from within the earth, as contrasted with a sedimentary rockwhich is a geologically deposited material. Basalt is igneous andbelongs to the salfemane group. It is close grained. The grains are toosmall to be readily distinguished by the eye but may contain largergrains of certain minerals interspersed in the dense material; that is,it may be ponphyritic.

Gabbro and diabase are much the same as basalt, but somewhat coarser, sothat grains of the constituent minerals are distinguishable to theunaided eye. Gabbro is noticeably granitoid. In the molten form gabbroand diabase are so nearly identical with basalt that either of them maybe used since it, is only necessary to adjust the heat treatment tocontrol the mineral constituents formed during the devitrifying cycle,Hence it is only necessary to determine the proper heat treatment togive the particular crystallization desired, the same crystallizationbeing obtained from either of the three forms of raw material.

It has been found by experiment that when basalt is used as an insulatorthat when an arc punctures the basalt partially fuses together or healsso that with arepeated are it will puncture along a new path, whereasporcelain, once punctured, will always flash through the same path.

The co-efficient of expansion of basalt is practically the same as iron,so that it may be cast around steel fittings with good bonding. Basaltmay be made to wet steel and does not require to be cemented to theinsulator fittings as does porcelain, quartz, or glass. As a resultthere is y no tendency for steel fittings, even under unusual heats, towork loose in basalt insulators or give any trouble such as is likely tooccur with porcelain, quartz or glass.

Accordingly, the present invention relates to the use of basalt orsimilar materials in connection with an improved spark plug ashereinbefore explained.

Other objects and advantages thereof will be more apparent from thefollowing description wherein several embodiments of the invention areillustrated.

In the drawing, Fig. l. is a vertical sectional view of one form ofmyimproved spark plug;

Fig. 2 is a cross-sectional view thereof taken generally on the line2-'2 of Fig. l;

Fig. 3 is a similar vertical sectional view of a modified form of theinvention, and i Fig. 4 is an elevational view of the basalt insulatorshown in Fig. 3.

Referring to Fig. 1, I have shown a spark plug which includes a casingor shell l0 formed with the hexagonal exterior walls I! for easymanipulation to mount the same in a suitable tapped opening of aninternal combustion engine. The lower portion of the shell I0 may bereduced and screw threaded as shown in H. The shell may have a body borel6, atapered wall portion 18 and reduced bore 20.

The insulator B may be formed of basalt or other igneous rock aspreviously described, and may comprise the enlarged body portion 22 andreduced upper and lower extremities 24 and 26. The body portion 22 maybe formed with the tapered walls 28 and 30. A metallic conductor 32having the protruding shaft portion 34 and the firing tip 36 is adaptedto be cast integral with the insulator B as will now be explained.

In the form of the invention thus far described, I contemplate theplacing of the shell I I] and the conductor 32 into a mold soconstructedthat molten basalt at proper'melting temperature may bepoured into the mold and take the shape shown in the drawing. In thismanner an eflicient one-piece spark plug has been provided with aninsulator having the same co-efficient of expansion as the shell l0 andthe conductor 32. As thus constructed the spark plug has no joints whichit is necessaryto seal and loss of compression in an internal combustionengine due to cracked or broken insulators as previously ex-' plainedwill be-an impossibility.

In the form of the invention shown in Figs. 3 and 4, I again cast aninsulator Bin the shape shown and provide the conductor 32 positioned inthe mold so that the insulator and conductor are cast integral. Theshell In may be generally similar to the one previously described,except that it is provided with an internal threaded bore 40 adjacentits upper end to receive a retainer nut 42 in the usual form to securelyhold the insulator B against the tapered shoulders l8. With thisconstruction it will be obvious that the spark plug can be made in theusual three pieces as is common in the art.

While I have shown and described a specific form of my invention and onemodified form thereof, it will be obvious to those skilled in the artthat many and varied changes may be made in the particular 'formthereof. The generic idea of the inve..tion is the provision of aninsulator for spark plugs or similar devices constructed of basalt orotherigneous rock material, and I do not wish to be limited in anyparticular, rather what I desire to secure and protect by Letters Patentof the United States is:

l. A spark plug having a metal shell, a-basalt insulator and a metalconductor mounted in said insulator.

2. A spark plug having a metal shell, a basalt insulator and a metalconductor mounted in said insulator, said insulator adapted to be moldedaround said conductor.

3. A spark plug comprising an elongated insulator of basalt, a conductorextending longitudinally through said insulator, a casing for saidinsulator and means for making a gas tight seal between said insulatorand said casing.

4. A spark plug for internal combustion engines comprising a metalshell, elongated insulating means therein consisting essentially of abasalt .material, a conductor therein having at one end a shaft, at theopposite end a firing tip and means including a retaining nut member forefiectively sealing said insulator in said casing.

5. A spark plug comprising an elongated insulator of basalt, a conductorextending longitudinally through said insulator, a casing forsaidinsulator and means comprising a retainer nut member friction-allyengaging said casing and bearing against a shoulder on said insulatorfor making a gas tight seal between said insulator and said casing.

6. A spark plug comprising an elongated insulator of basalt, saidinsulator formed with an enlarged body portion, tapered upper and lowerwalls thereon and reduced cylindrical extremities extending therefrom, aconductor extending longitudinally through said insulator, a casing forsaid insulator, said casing having a tapered ledge upon which the lowerwall of said insulator body portion rests and means for making a gastight seal between said insulator and said casing.

7. A spark plug comprising a basalt insulator member, a conductor in theform of a metal rod passing longitudinally therethrough and a shellmember for mounting said spark plug on an internal combustion motoradapted to be cast integral with said insulator.

8. A spark plug comprising a basalt insulator member, a conductor in theform of a metal rod passing longitudinally therethrough and a shellmember for mounting said spark plug on an internal combustion motor,said shell and conductor adapted to be held i mold and said basalt in amolten condition integral therewith.

ADDISON C. HOOP.

